This invention was made with government support under grant number DMR-0520513 awarded by the National Science Foundation. The government has certain rights in the invention.
Materials that store textual and/or graphical information for a prescribed period of time are desirable for applications in secure communications. Furthermore, if such materials are rewritable, they can help to limit the use of traditional paper, thereby reducing the costs, both industrial and environmental, associated with paper production and recycling.
Most research on self-erasing media has relied on the use of photochromic molecules—that is, molecules that isomerize and change color when exposed to light of appropriate wavelength—embedded in or attached to a polymeric/gel matrix. In one widely publicized example, Xerox Corporation has recently announced the development of photochromic paper that self-erases within 16 to 24 hours. While writing with light can be both rapid and accurate, photochromic “inks” are not necessarily optimal for transforming light-intensity patterns into color variations because they have relatively low extinction coefficients, are prone to photobleaching, and usually offer only two colors corresponding to the two states of photoisomerizing molecules.